"If we find a relationship between consumption of the product and harm, FDA will take appropriate action to reduce or eliminate the risk," the FDA said. "While the FDA investigates all reports to the best of its ability, it does not always have access to all the information needed to conclusively determine the cause of the event."

While much more investigation is needed, early speculation points to the way in which consumers may be misusing the product. With a reported 207 mg of caffeine in one 5-hour ENERGY shot, consuming multiple servings in a day could be dangerous, especially for people who have underlying health conditions.

The makers of 5-hour ENERGY, Living Essentials LLC, said in a statement: "We recommend on product labels and the 5-hour ENERGY website that individuals consume no more than two bottles of 5-hour ENERGY shots per day, spaced several hours apart."

Still, these high-caffeine beverages make me really nervous, especially when kids and teens drink them like soda and don't think about the consequences. I stay away from them, and opt for more natural energizers.